The United States has announced its departure from the United Nations’ main human rights body as President Donald Trump faces increasing criticism for his policy of separating migrant families.

Secretary of State, Mike Pompeo, and US Ambassador to the United Nations, Nikki Haley, delivered the verdict on the UN Human Rights Council in a joint appearance at the State Department on Wednesday (AEST).

In announcing the US withdrawal, Ms Haley issued a blistering critique of the panel, saying it has become “protector of human rights abusers, and a cesspool of political bias”.

“I want to make it crystal clear that this step is not a retreat from our human rights commitments,” she said.

“On the contrary. We take this step because our commitment does not allow us to remain a part of a hypocritical and self-serving organisation that makes a mockery of human rights.”

Ms Haley said the decision to leave the 47-nation body came after governments with poor human rights records aspired to gain  a seat on the council to avoid scrutiny and then resisting proposals for reform.

“When we made it clear we would strongly pursue Council reform, these countries came out of the woodwork to oppose it,” she said.

“Russia, China, Cuba, and Egypt all attempted to undermine our reform efforts this past year.”

She also cited the admission of Congo as a member despite mass graves being discovered there, and the failure to address human rights abuses in Venezuela and Iran as a reason for the US’ withdrawal.

The departure comes as Mr Trump defended the contentious removal of refugee children from their parents, accusing the Democrats of wanting migrants to “infest our country”.

Mr Trump used language evoking images of pests, not human beings, in an overnight tweet describing migrants approaching the US border.

“Democrats are the problem,” he wrote.

“They don’t care about crime and want illegal immigrants, no matter how bad they may be, to pour into and infest our Country, like MS-13. They can’t win on their terrible policies, so they view them as potential voters!” he wrote.

Democrats are the problem. They don’t care about crime and want illegal immigrants, no matter how bad they may be, to pour into and infest our Country, like MS-13. They can’t win on their terrible policies, so they view them as potential voters!

— Donald J. Trump (@realDonaldTrump) June 19, 2018

The President’s rhetoric follows intense criticism of his migrant policy after photos emerged of caged children in a warehouse detention centre and harrowing audio was leaked of families separated at the US border.

The US is halfway through a three-year term on the main UN rights body and had long threatened to quit if it was not reformed, accusing the 47-member Geneva-based body of being anti-Israel among other things.

UN High Commissioner for Human Rights Zeid Ra’ad al-Hussein has called on Washington to halt its “unconscionable” policy of removing migrant children from their families.

Foreign Minister Julie Bishop said Wednesday that Australia shares many concerns held by the US about the UN Human Rights Council, but would not be pulling out.

“We are committed to progress effective and meaningful reform to enable the council to more effectively carry out its role,” Ms Bishop said in a statement.

“It was our strong preference for the US to remain a member of the UNHRC and I had made this known to senior members of the Trump administration.”

Washington’s pull-out is the latest US rejection of multilateral engagement after it pulled out of the Paris climate agreement and the Iran nuclear deal.

More than 2000 children have been separated from their families since ‘zero tolerance’ on migrants was declared. Photo: US Customs and Border Patrol

Decrying “internment camps,” opposition politicians and their supporters disrupted a high-profile US congressional hearing on Wednesday morning (AEST), with a protest against the Trump administration’s policy of detaining immigrant children.

With the sound of a young child crying in the background, the top Democrat on the House of Representatives Judiciary Committee, Jerrold Nadler, broke from protocol to read from a statement saying “these children are not animals.”

His Republican colleagues tried to shout over him “Out of order!”

Congressman Elijah Cummings, the top Democrat on the House Oversight Committee blasted what he called a policy of putting children into “internment camps,” and called on Republicans to stand up against the president.

“We should be able to agree that we will not keep kids in child internment camps indefinitely and hidden away from public view. What country is that? This is the United States of America!,” a visibly emotional Mr Cummings said.

“Mr. Chairman, we need you. Those children need you,” he said.

“I am talking directly to my Republican colleagues. We need you to stand up to President Trump. We need you to join us in telling him that we reject this mean policy.”

The separations began after US Attorney General Jeff Sessions announced a “zero tolerance” policy in April in which all those apprehended entering the United States illegally would be criminally charged.

Criticism of the treatment of the children has intensified in recent days. On Tuesday, the attorneys general of 21 states called on Mr Sessions in a letter to stop endangering children by separating them from their families.

“Put simply, the deliberate separation of children and their parents who seek lawful asylum in America is wrong. This practice is contrary to American values and must be stopped,” the attorney general in the border state of New Mexico Hector Balderas said.

-with agencies